320 



Dr. Pickering observed that he believed the Cypris, a minute 

 crustacean with a kind of bivalve shell, secreted siliceous mat- 

 ter ; at any rate they were so hard as to scratch glass, and it vi^as 

 difficult to examine them under the microscope without great 

 care. 



Dr. Burnett gave an account of some observations vs^hich 

 he had made on the atmospheric dissemination of algous 

 plants. 



The occurrence of minute Algse and Spores in liquids and 

 infusions, under circumstances rendering improbable their intro- 

 duction from without, is frequently noticed by the microscopical 

 observer. 



While making experiments upon Diabetic Urine, (the abun- 

 dant presence in which of the common ferment Alga, Torula 

 cerevisicB is well known,) he was surprised to find all the com- 

 mon liquids in its neighborhood pervaded by this same Alga, 

 and particularly those exhibiting any tendency to decomposition. 

 This led him to think that the dissemination of this minute plant 

 took place by the medium of the atmosphere, which was full of 

 its spores. 



Experiments with air tight and partially covered vessels of 

 liquid, placed near the original source, showed this to be true. 

 And even for several weeks after, the atmosphere of the room 

 seemed to retain many of the spores ; for liquids placed as 

 before soon contained many of the plants. 



He stated this fact on account of the too great importance 

 often attached to the presence of fungi and algs in various local- 

 ities, and especially as being tlie cause of various coincident 

 phenomena; whereas, their presence may, in many cases, be 

 considered accidental. 



Dr. C. T. Jackson alluded to experiments of passing the air 

 containing these fungi through concentrated sulphuric acid. No 

 infusoria were found in vessels to which air could only gain 

 admittance to a vegetable infusion through this medium, while 

 they were abundantly found in infusions to which air had free 

 access. These results confirmed the statements of Dr. Burnett. 



